1. Technical Field
The present invention generally relates to transistors. More particularly, the present invention relates to light-responsive field effect transistors.
2. Background Information
In the past, light-responsive field effect transistors or optical FETs have been limited in usefulness, due to the size thereof and the limited voltage provided thereby, which may be inadequate for some applications. One example of such an optical FET can be found in U.S. Pat. No. 4,841,349 issued to Nakano, and entitled "Semiconductor Photodetector Device With Light Responsive PN Junction Gate." Nakano discloses an optical FET with a gate extension, forming a PN junction lying in a vertical plane. See FIG. 2 of Nakano. Although the gate extension and vertical junction of Nakano may help reduce the amount of light impinging on the channel region, the Nakano gate extension uses up valuable chip real estate and requires more processing than may be necessary. In addition, the voltage produced by a single junction in response to light impinging thereon may be inadequate for some applications.
Thus, a need exists for an optical FET that minimizes the use of real estate and the number of processing steps, while providing a customizable voltage in response to light.